Flame retardant polyolefin composition of improved color and melt stability

ABSTRACT

Flame retardant polyolefin compositions having improved color and melt stability are obtained by the addition of a phenolic stabilizer and a metal soap mixture to said compositions.

v United States Patent Mathis June 28, I974 FLAME RETARDANT POLYOLEFIN COMPOSITION OF IMPROVED COLOR [56] References Cited AND MELT STABILITY UNITED STATES PATENTS [75] Inventor: Ronald D. Mathis, Taylors, S.C. 2,903,487 9/1959 Coffield 260/45.75 B 3,075,944 1/1963 Wiek et a1 260/4575 B [73] Asslgnee: g fif gif Company 3,244,650 4/1966 Hecker et a1. 260/23 H ar esvr e, a.

[22] Filed: Apr. 17, 1972 Primary Examiner-Donald E. Czaja l 1 pp N 244 894 Assistant Examiner-Eugene C. Rzucidlo [57] ABSTRACT [52] g Flame retardant polyolefin compositions having im- 260/45'95 proved color and melt stability are obtained by the addition of a phenolic stabilizer and a metal soap mix- [5 1] Int. Cl. C08f 45/58, C08f 45/62 ture to Said compositions [58] Field of Search... 260/23 H, 45.75 B, 45.85 R,

260/4595 J, 45.7 P, 45.95 G, 45.95 R

14 Claims, N0 Drawings 1 FLAME RETARDANT POLYOLEFIN COMPOSITION OF IMPROVED COLOR AND MELT STABILITY This invention relates to flame retardant polyolefln compositions and to methods for the preparation of same.

Flame retardant polyolefin compositions are highly desirable raw materials for manufacture of various compression and injected molded items such as plastic pipe, rods, sheets, and the like. ln the formulation of flame retardant polyolefln compositions it has been generally found that these polyolefln compositions exhibit undesirable color and melt degradation at temperatures commonly employed in molding and extruding said compositions into finished articles of manufacture. Accordingly because of the economic advantage and in most cases the economical necessity of employing thermally stable polymer compositions of widely varying colors in the production of plastic articles, means for improving the melt and color stability of flame retardant polyolefln compositions is desirable. However many commercial stabilizers lose a significant part of their effectiveness when combined with flame retardants.

It is an object of this invention to provide flame retardant polyolefln compositions that exhibit improved melt flow processing characteristics. Still another object is to provide flame retardant polyolefln composi tions of improved color stability. Still further it is an object to provide both melt and color stable flame retardant polyolefln compositions. Other objects of this invention will be apparent from the written description and the appended claims.

According to this invention, flame retardant polyolefin compositions are stabilized against undesirable color and melt degradation by the addition of a phenolic stabilizer and a metal soap mixture to said compositions.

The polyolefins that can be employed in the practice of this invention are homopolymers and copolymers derived from the polymerization of l-monoolefins having from two to eight carbon atoms. In most instances, the preferred polyolefins are homopolymers of ethylene or propylene copolymers of ethylene with minor amounts of other monomers copolymerizable therewith such as propylene, butene-l, hexene-l, octene-l and the like, or copolymers of propylene with minor amounts of other monomers copolymerizable therewith such as ethylene, butene-l, hexene-l, octene-l, and the like. Polyoleflns wherein at least 50 mol percent of the polyolefln is derived from the polymerization of ethylene or propylene monomeric units are presently preferred. Even more preferred are polyolefins wherein at least 90 mol percent of the polyolefin is derived from the polymerization of ethylene or propylene monomeric units. Still even more preferred because of their commercial importance are propylene polymers wherein at least 90 mol percent of the polyolefin is derived from the polymerization of propylene and from about 0.5 to 10 mol percent of the polyolefin is derived from the polymerization of a comonomer selected from ethylene or butene-l.

The flame retardant additives that can be employed in the practice of this invention are halogenated organic compounds, preferably halogenated ethers. Preferred halogenated ethers include acyclic and cyclic hydrocarbyl ethers which contain from eight to 22 car- 2 boni atoms and can be represented by the following general formula:

wherein X and Y individually represent acyclic and cyclic hydrocarbyl radicals at least one of which is partially halogenated. Preferably the hydrocarbyl radicals are selected from aliphatic, cycloaliphatic, and aromatic radicals or combinations thereof. Particularly preferred halogenated ethers are mixed alkyl aryl ethers wherein the aryl hydrocarbon group contains from six to 15 carbon atoms and the alkyl group contains from three to 12 carbon atoms. Representative halogenated mixed alkyl aryl ethers include 2,3- dibromopropyl 2,4,6-tribromophenyl ether, 11,12- dibromododecyl 2,6-dibromo-4-n-octylphenyl ether, 2,4,6-tribromophenyl benzyl ether, 3,4-dibromobutyl phenyl ether, 2,4,6-tribromophenyl cyclohexyl ether, 2,2-bis[4-(2,3-dibromopropoxy)phenyl]propane, 2,2- bis-[4-(2,3-dibromopropoxy)3,5- dibromophenyl1propane, and mixtures thereof.

Metaloxides can be employed in conjunction with halogenated organic compounds to improve the efflcacy of the flame retardant additives. Representative metal oxides include arsenic trioxide, antimony trioxide and bismuth trioxide. Antimony oxide, preferably as the trioxide, is preferably employed with the halogenated ether.

The phenolic stabilizers that can be employed in the practice of this invention can be described by the formula:

wherein each R represents an alkyl radical, and individually each R radical contains from one to eight carbon atoms. Representative of suitable commercially available phenolic stabilizers include 2,4,6-trimethylphenol, 2,6-diethyl-4-methylphenol, 2,4-dimethyl-6-tbutylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-amyl-4-hexylphenol, 2,6-di-t-octyl-4-noctylphenol, 2,4,6-tri-t-butylphenol, and the like. Generally preferred phenolic stabilizers contain at least two tertiary alkyl radicals. Presently preferred phenolic stabilizers are 2,6-di-t-alkyl-4-methylphenols. Especially preferred is the 2,6-di-t-butyl-4-methylphenol.

The metal soap mixtures employed in the practice of this invention comprise a mixture of a polyvalent metal soap, a polyvalent metal phenolate, and a triaryl phosphite. The polyvalent metal soaps can be represented by the formula (RCOO) M, wherein each R is a cyclic or acyclic hydrocarbyl radical, individually each R radical contains from seven to 22 carbon atoms, and M is selected from the polyvalent metals barium, cadmium,calcium, lead, strontium, tin and zinc. Presently preferred are polyvalent metal soaps wherein M is barium cadmium or zinc, and mixtures thereof. The pol yvalent metal phenolates can be represented by the formula M(OR") wherein each R" is an aryl or alkaryl hydrocarbyl radical, individually each R" radical contains from four to l8 carbon atoms, and M is the same as represented hereinbefore. The triaryl phosphites can be selected from triaryl phosphites containing eight to 22 carbon atoms.

The improved flame retardant polyolefin composipracticing invention, which accordingly are not to be considered as unduly limitative.

tions of this invention comprise any composition con- EXAMPLE I taining a polyolefin, a halogenated organic compound, 5 a Phehohe stablhlel', hf a metal 9 p mixture Various flame retardant polyolefin compositions Preferred eomposlhohs eohtam on a Welght b21515 were prepared containing a phenolic stabilizer, or a P 100 Parts Of Polyolefih at least 0005 P e phenolic stabilizer and a metal soap mixture. The com- Preferably from 0005 to Part5, Ofa PhehOhe Stablpositions were separately dry blended by tumbling in a hZer; at least paftqmore Preferably from to closed container for 30 minutes, and subsequently mas- P Of metal p mlxtufe; at least 1 Part, more P ticated in a Brablender plastograph at 200C for 5 minerably from 1 to Parts, Of halogenated Organ? utes under a nitrogen atmosphere. The chemical con- Pouhdmtleast Part, more Preferably 1O stituents of the various compositions are set out in P 15 of metal OXlde- More Preferred e P h Table l. The polymer compositions of Table I, set out tam from t0 parts Of phenolic stab1l1zer; from 15 hereafter were ubsequently evaluated melt flow t0 Parts Of metal 9 p mlXtUre; from t0 5 extrudate tests wherein the weight of polyolefin comparts of halogenated orgamc Compound; and from position extruded, under a 268.5 gram load, during a to Parts of metal oxldeone-minute time interval was measured after a 5 minhl e P p e e e flame Tetardaht p el ute and a 10 minute pre-extrusion time residence pecompos1t1ons of this invention, the phenoltc stabtltzers 2O i d at 490]: i accordance ith ASTM D 1238-621 and metal Soap m tureS Can be COmbmed Wlth a halO- condition L test procedure. The extrudate temperature gehated otgamc Compound d Polyolehn y e h was also 490F. The melt flow extrudate test data is set of y shltfible Process, P i g the Process hout in Table II. In addition, the polyolefin extrudate "l y aflmlxes all of e Ingredients of h p compositions were compression molded into small disttons. Su1table processes include dry blending of the 1n- 25 yes, one i h i diametgpby 1/16-i h thi k a d l r grediehts of the QmPP S 1n subdwtded form and rated against a standard color scale wherein a numeri- Subsequently masheahhg the hg admlxhlre at cal value of 1 indicates a clean bright yellow color, inpe y melt temperatures for a Pehod of hme $ufh' creasing numerical values indicate increasing green dis- Clenl to form homogeneous polyolehn e p coloration, and a numerical value of 5 indicates green- 56! Out hereinafter are examples Whleh llhlstfate black discoloration. The color rating data is set out in invention, lncluded are examples of the best motor T bl [1,

TABLE I Run Number l 2 3 4 5 6 7 Chemical Ingredients, by weight Polyolefin 100 100 100 100 100 100 100 Halogenated Organic Compound 2 2 2 2 2 2 2 Metal Oxide l l l l l l l Phenolic Stabilizer-l 0.1 0.1 0.5 Phenolic Stabilizer-2" 0.5 0.5 0.5 Phenolic Stabilizer-3 0.5 0.5 Metal Soap Mixture 0.5 0.5 0.5 0.5 0.5 Pigment l l l l l l i TABLE II Melt Flow Extrudate Values Extrudate Test Conditions Pre-extrusion Temp. F/Min.

490/5 min. 0065 0.047 0.094 0.074 0.044 0.063 0.045 490/10 min. .083 .078 .339 .159 .053 .132 .058

Color Ratings 49075 min. 1.75 1.75 1.25 1.25 1.25 1.50 1.25 490710 min. 2.25 2.00 1.75 1.75 1.25 1.75 1.25

(:11 Polypropylene containing trace quantities, 1.1.-., less than 0.02 part of 2,6-di-t-hutyl-4-methylphenol per 100 parts of polypropylene.

(b) 2.3-!)ibr11moprt1pyl 2,4.(1-trihrumophenyl ether 1c) Antimony lHUXlllt:

ttl) ()etndeeyll Ll Ll,5-tli-t-butyl-4-hydroxyphcnyl)lprupionutc (l) Nickel bist()-uthoxy-3,5-di-t-butyl-4-hydroxybenzylphosphonateJ (g) l.1q111ti mixture of barium. cudmiu1n nnd zinc eurhoxylutes and ulkylphenulntcs, and u trinryl phosphite the elemental analysis being about 6.2 wt. percent barium, about 2 l wt. percent entlntiuni, tihuut l.3 wt. percent zinc and about |.5 wt. percent phosphorus (l1) Yellou .lti (dis ersion form, i.e. 25'71 pign1ent-- '71 polypropylene, by weight) The above melt flow data illustrates that the melt stability of flame retardant polyolefins is improved by the presence of a metallic soap mixture and a phenolic stabilizer, and is particularly improved by the combined presence of a metallic soap mixture and a phenolic stabilizer of Formula I specifically described elsewhere in this specification.

The above color rating data illustrate that both the melt flow stability and the color stability of the flame retardant polyolefin compositions are improved concurrently by the present of a metal soap mixture and a phenolic stabilizer of Formula 1.

Further modifications of the teachings of this invention by the use of phenolic stabilizers and metal soap mixtures to impart improved melt and color stability to flame retardant polyolefin compositions will be apparnet to those skilled in the art.

That which is claimed is:

l. A flame retardant composition consisting essentially of a polyolefin selected from homopolymers and copolymers derived from the polymerization of lmonoolefins having from two to eight carbon atoms, a halogenated ether selected from the group consisting of acyclic and cyclic hydrocarbyl ethers which contain from eight to 22 carbon atoms, a phenolic stabilizer having the formula: (I)

wherein each R represents an alkyl radical, and a metal soap mixture containing a polyvalent metal soap having the formula wherein each R is a cyclic or acyclic hydrocarbyl radical, M is selected from polyvalent metals barium, cadmium, calcium, lead, strontium, tin and zinc, a polyvalent metal phenolate having the formula wherein M is the same as represented hereinbefore, and R" is an aryl or alkylaryl hydrocarbyl radical, and a triaryl phosphite.

2. A composition in accord with claim 1 wherein the ether is represented by the formula:

wherein X and Y, individually, are selected from the group consisting of acyclic and cyclic hydrocarbyl radicals and partially halogenated acyclic and cyclic hydro-' carbyl radicals, and wherein at least one of X and Y is a partially halogenated acyclic or cyclic hydrocarbyl radical.

3. A composition in accord with claim 2 wherein the composition contains on a weight basis, per 100 parts of said polyolefin, from about 1 to about parts of said halogenated ether, from about 0.005 to about 2.5 parts of said phenolic stabilizer, and from about 0.] to about 2.5 parts of said metal soap mixture.

4. A composition in accord with claim 3, wherein the composition contains a metal oxide selected from oxides of arsenic, antimony, and bismuth.

5. A composition in accord with claim 4 wherein the composition contains on a weight basis, per l00 parts of said polyolefin, from about 0.5 to about 10 parts of said metal oxide.

6. A composition in accord with claim 5, wherein said polyolefin is polypropylene.

7. A composition in accord with claim 6, wherein said phenolic stabilizer is 2,6-di-t-butyl-4- methylphenol, said metal soap mixture contains the metals barium, cadmium, and zinc, said halogenated ether is 2,3-dibromopropyl 2,4,6-tribromophenyl ether, and said metal oxide is antimony trioxide.

8. A method of preparing a flame retardant polyolefin composition having improved melt and color stability which consists essentially of (l) a polyolefin selected from homopolymers and copolymers derived from the polymerization of l-monoolefins having from two to eight carbon atoms; (2) a halogenated ether selected from the group consisting of acyclic and cyclic hydrocarbyl ethers which contain from eight to 22 carbon atoms; (3) a phenolic stabilizer having the formula:

wherein each R represents an alkyl radical; (4) a metal soap mixture containing a polyvalent metal soap having the formula mium, calcium, lead, strontium, tin and zinc; (5) a polyvalent metal phenolate having the formula wherein M is the same as represented hereinbefore, and R is an aryl or alkylaryl hydrocarbyl radical; and (6) a triaryl phosphite; which comprises admixing said polyolefin, said halogenated ether, said phenolic stabilizer, said metal soap mixture, said polyvalent metal phenolate, and said triaryl phosphite; and thereafter forming the resulting admixture into a molded or extruded flame retardant polyolefin composition by masticating the resulting admixture at polyolefin melt temperatures for-a period of time sufficient to form a homogeneous polyolefin composite.

9. A method in accord with claim 8 wherein the ether is represented by the formula:

wherein X and Y, individually, are selected from the group consisting of acyclic and cyclic hydrocarbyl radicals and partially halogenated acyclic and cyclic hydrocarbyl radicals, and wherein at least one of X and Y is a partially halogenated acyclic or cyclic hydrocarbyl radical.

10. A method in accord with claim 9 wherein the composition contains on a weight basis, per parts of said polyolefin, from about 1 to about 20 parts of said halogenated ether, from about 0.005 to about 2.5 parts of said phenolic stabilizer, and from about 0.] to about 2.5 parts of said metal soap mixture.

11. A method in accord with claim 10 wherein the composition contains a metal oxide selected from the 14. A method in accord with claim 13 wherein said phenolic stabilizer .is 2,6-di-t-butyl-4-methylphen0l, said metal soap mixture contains the metals barium,

cadmium, and zinc, said halogenated ether is 2,3-'

dibromopropyl 2,4,6-tribrom0phenyl ether, and said metal oxide is antimony trioxide. 

2. A composition in accord with claim 1 wherein the ether is represented by the formula: X - O - Y wherein X and Y, individually, are selected from the group consisting of acyclic and cyclic hydrocarbyl radicals and partially halogenated acyclic and cyclic hydrocarbyl radicals, and wherein at least one of X and Y is a partially halogenated acyclic or cyclic hydrocarbyl radical.
 3. A composition in accord with claim 2 wherein the composition contains on a weight basis, per 100 parts of said polyolefin, from about 1 to about 20 parts of said halogenated ether, from about 0.005 to about 2.5 parts of said phenolic stabilizer, and from about 0.1 to about 2.5 parts of said metal soap mixture.
 4. A composition in accord with claim 3, wherein the composition contains a metal oxide selected from oxides of arsenic, antimony, and bismuth.
 5. A composition in accord with claim 4 wherein the composition contains on a weight basis, per 100 parts of said polyolefin, from about 0.5 to about 10 parts of said metal oxide.
 6. A composition in accord with claim 5, wherein said polyolefin is polypropylene.
 7. A composition in accord with claim 6, wherein said phenolic stabilizer is 2,6-di-t-butyl-4-methylphenol, said metal soap mixture contains the metals barium, cadmium, and zinc, said halogenated ether is 2,3-dibromopropyl 2,4,6-tribromophenyl etheR, and said metal oxide is antimony trioxide.
 8. A method of preparing a flame retardant polyolefin composition having improved melt and color stability which consists essentially of (1) a polyolefin selected from homopolymers and copolymers derived from the polymerization of 1-monoolefins having from two to eight carbon atoms; (2) a halogenated ether selected from the group consisting of acyclic and cyclic hydrocarbyl ethers which contain from eight to 22 carbon atoms; (3) a phenolic stabilizer having the formula:
 9. A method in accord with claim 8 wherein the ether is represented by the formula: X - O - Y wherein X and Y, individually, are selected from the group consisting of acyclic and cyclic hydrocarbyl radicals and partially halogenated acyclic and cyclic hydrocarbyl radicals, and wherein at least one of X and Y is a partially halogenated acyclic or cyclic hydrocarbyl radical.
 10. A method in accord with claim 9 wherein the composition contains on a weight basis, per 100 parts of said polyolefin, from about 1 to about 20 parts of said halogenated ether, from about 0.005 to about 2.5 parts of said phenolic stabilizer, and from about 0.1 to about 2.5 parts of said metal soap mixture.
 11. A method in accord with claim 10 wherein the composition contains a metal oxide selected from the oxides of arsenic, antimony, and bismuth.
 12. A method in accord with claim 11 wherein the composition contains on a weight basis, per 100 parts of said polyolefin, from about 0.5 to about 10 parts of said metal oxide.
 13. A method in accord with claim 12 wherein said polyolefin is polypropylene.
 14. A method in accord with claim 13 wherein said phenolic stabilizer is 2,6-di-t-butyl-4-methylphenol, said metal soap mixture contains the metals barium, cadmium, and zinc, said halogenated ether is 2,3-dibromopropyl 2,4,6-tribromophenyl ether, and said metal oxide is antimony trioxide. 